Double telescoping hydraulic prop



Jan. 31, 1967 a. DOMMANN ETAL 3,301,519

DOUBLE TELESCOPING HYDRAULIC PROP Filed Oct. 18, 1965 5 Sheets-Sheet 1IN VE N TOPS:

GUNTHER DUMMANN. ERICH HUFFMANN MANFREU FLUTER. EGUN WARNS Jan. 31, 1967G. DOMMANN ETAL 3,301,519

DOUBLE TELESCOPING HYDRAULIC PROP Filed Oct. 18, 1965 5 Sheets-Sheet 2INVENTOPS: GUNTHER UOMMANN, ERIEH HUFFMANN, MANFRED FLUTER, EGUN WARNSJan. 31, 1967 DOMMANN ETAL, 3,301,519

DOUBLE TELESCOPING HYDRAULIC PROP Filed Oct. 18, 1965 5 Sheets-Sheet :5

Fig. 5

IN VE N TOPS:

BUNTHER DOMMANN ERIEH HUFFMANN, MANFRED FLUTER, GUN WARNS United StatesPatent 3,301,519 DOUBLE TELESCOPING HYDRAULIC PROP Gunther Dommann andErich Hoiimann, Altlunen, Manfred Floter, Lunen, and Egon Warns,Wethmar, Germany, assignors to Gewerkschaft Eisenhutte Westfalia,Wethmar, near Lunen, Germany, a corporation of German Filed Oct. 18,1965, Ser. No. 496,822 Claims priority, application Germany, Oct. 20,1964, G 41,819 20 Claims. (Cl. 248354) This invention rel-ates to doubletelescoping hydraulic props. It more particularly refers to such propswhich are more reliable and have greater constancy of operation thanthose of the prior art.

Double telescoping hydraulic props are well known. They are usedextensively in mining operations to hold up the mine tunnel roof. Ingeneral these devices provide a cylinder housing two telescoping pistonsarranged in such manner that both pistons are activated and moved from asingle source by a single hydraulic fluid.

Because of the fact that the two pistons telescope, they present adiiferent surface area to the pressurizing hydraulic fluid; the insidepiston has a smaller working face surface area than does its surroundingoutside piston. For ease of understanding, the outside piston may behereinafter referred to as the first stage and the inside piston may behereinafter referred to as the second stage.

As generally noted above, the single hydraulic fluid is capable ofacting on both the first and second stages :at the same time. Since thefirst stage has a larger working surface, it will tend to be projectedin preference to the second or inside stage.

Double telescoping hydraulic props are generally constructed in such amanner as to permit the first or outer stage to be hydraulicallyextended to a maximum point predetermined by means of a stop or shoulderextending inwardly from the top of the encasing cylinder a distancesuflicient to engage a shoulder or flange which extends outwardly fromthe base of the first stage. When these two shoulders engage, the firststage is prevented from further extension without fracture of at leastone of these two shoulders. Similarly, the top of the first stage has aninwardly extending shoulder to engage and mate with an outwardlyextending shoulder of the base of the second stage for the same purpose.A space is defined by the combination of the inside cylinder wall, theoutside of the first stage piston, the first stage base shoulder and thecylinder top shoulder; similarly a space is defined by the combinationof the inside wall of the first stage piston, the outside wall of thesecond stage piston, the second stage base shoulder and the first stagetop shoulder. Such spaces are known to the prior art and have been usedto retract the pistons under positive hydraulic pressure as desired.

In the operation of prior art double telescoping hydraulic props, it wasthe practice to fully extend the first stage piston to the engagement ofthe first stage piston base shoulder with the cylinder top shoulder andthence to extend the second stage piston by continued hydraulic pressureuntil its top met and engaged the mine tunnel roof. Upon engagement withthe roof, additional hydraulic pressure was provided to set the propagainst the roof. Thus, the magnitude of the holding or setting force ofthe prop was determined by the pressure of the hydraulic fluid on thesmaller (second stage) piston.

When it was required to move the prop to a different location, thehydraulic fluid pressure was relieved or released thus causing thepiston assembly to retract from the roof and permit the total device tobe moved. As will be apparent, upon relief or release of the pressureacting upon the pistons, the first stage piston was the first to retractwith the relation between the first and second stage pistons remainingsubstantially constant until the first stage has been fully retracted.

In many instances, the piston assembly is not fully retracted since itis to be used very shortly and very near to the place where it waspreviously used. Thus, when the prop is now reused in a differentlocation, hydraulic fluid pressure is again exerted on the doublepistons and the outer stage is the first to extend until as before thecylinder and first stage shoulders engage. Now, if the new location ofuse offers a floor to roof dimension less than that of the old or priorlocation of use, the first stage will not extend fully to the shoulderengagement since the top of the second stage will have met the roof andwill have become set through the additional hydraulic fluid pressure.

It should be noted at this point that the setting forces of the twoinstallations just described are different even if the hydraulic fluidpressure is the same since in the first case the setting force wasaccomplished by action of the hydraulic fluid against the smaller secondstage piston whereas in the latter case the setting force wasaccomplished by action of the hydraulic fluid against the larger firststage piston.

As can be appreciated, these same principles apply where more than two,e.gl three or more, stages are employed. It will also be appreciatedthat though the term cylinder has been employed, it is used in itsgeneric functional sense and is not intended to be limited to anyparticular geometric shape.

It is an object of this invention to provide a multiple telescoping propwhich is not subject to the disadvantages of prior art systems.

It is another object of this invention to provide a multiple telescopingprop system which will always provide the same setting force regardlessof the floor to roof dimension of the space in which it is acting.

It is a further object of this invention to provide a multipletelescoping prop which will always provide a setting force determined bythe largest piston face in the assembly.

It is still another object of this invention to provide a multipletelescoping pr'op which will always provide a setting force which is themaximum for the particular geometric configuration of the particularprop utilized.

Other and additional objects of this invention will be apparent from theconsideration of this entire specification including the drawing and'the claims.

In accord with and fulfilling these objects, this invention comprises amultiple telescoping hydraulic activated prop so arranged that thelargest, and each succeeding smaller stage except the smallest, isphysically prevented from extending to its maximum prior to its nextsmallest stage having extended to its maximum until the top of thesmallest stage engages and contacts the roof to be supported by the propand then providing the setting force to hold the top of the smalleststage against the roof by action of the hydraulic fluid pressure uponthe largest stage piston.

This invention will be better understood with reference to the drawingin which:

FIG. 1 is a front elevation partially in section, with parts brokenaway, of a device according to this invention;

FIG. 2 is a front elevation of a slightly modified device according tothis invention;

FIGS. 3 and 3a are similar to FIG. 2 showing further modified forms ofthis invention;

FIG. 4 is similar to FIG. 1 showing the hydraulic fluid circulationsystem of a device according to this invention; and

FIG. is a full front elevation partially in section of the device shownin FIG. 4.

Referring now to the drawings and particularly to FIG. 5 thereof, adouble telescoping hydraulic prop is shown having a cylinder 1 encasinga first stage piston 5 and a second stage piston 11). The first stagepiston base 15 and the base of the cylinder 33 together with the insidewalls of the cylinder define a space 25 into which hydraulic fluid canbe pumped through an orifice 31.

A similar space 30 into which hydraulic fluid can be pumped to act upona second stage piston is defined by the inside walls of the first stagepiston 5, the top of the first stage piston base and the base 14 of thesecond stage piston 10. Hydraulic fluid will be admitted into this space30 through a valve 26 in the first stage piston base .15.

Under normal (prior art) operation, when hydraulic fluid is admittedthrough the orifice 31 into the chamber 25 the first stage piston 5would be extended until the shoulder 19 at the base thereof met theshoulder stop 16 at the top of the cylinder 1. Additional or continuedhydraulic pressure would then cause the space 30 to fill therebyextending the second stage piston 10 until it engaged with the roof tobe supported.

Upon release of hydraulic pressure, the hydraulic fluid will drain outof space 25 first thus causing the first and second stages to retract asa single unit. Upon complete retraction of this unit, the hydraulicfluid from the space 30 would then drain permitting the second stage toretract with reference to the first stage.

According to this invention however, physical means are provided torestrain the first stage from expanding to its maximum.

Referring now to FIG. 1, it can be seen that the first stage 5 can beprevented from extending to its maximum by providing a chain 3 or otherextension device from a flange 4 on the first stage 5 to a flange orother extension 2 on the cylinder. A modification of this is shown inFIG. 2 where the chains 3 are attached to the cylinder 1 by means ofsprings 6 so as to prevent or at least reduce the tendency for thechains 3 to snap under the tension caused by the hydraulic pressure.

In FIGS. 3 and 3a a different arrangement is shown to accomplish thesame purpose of preventing the first stage from extending to its maximumbefore extending the second stage. In this embodiment the flange 4 has aguard jacket 7 attached thereto. The bottom of the guard jacket 7 has abrake collar 8 thereon which is adjustable in its braking effect bymeans of lever 9 which may be a tensioning device, a set screw or thelike. Thus the first stage piston is prevented from extending by meansof this brake collar. In FIG. 3a the guard jacket 7 has been replaced bylead screws 11 which are adjustable to position the distance from thebrake collar to the flange 4.

In employing any of the embodiments of this invention shown in FIGS. 1through 3a, the first stage piston is prevented from extending to itsmaximum prior to the extension of the second stage piston. When thesecond stage piston extends sufliciently to have contacted the roof, thestopping device is either released, in the case of the chain 3 of FIG. 1or the spring 6 of FIG. 2, or it may be overridden, as in the case ofthe brake collar 8 of FIGS. 3 and 3a.

Upon release or overriding of the stopping device, the hydraulic fluidpressure is then free to act upon the first stage causing it to extendslightly further and thereby exerting the setting force necessary tosupport the roof.

If desired, stops 13 can be provided on the cylinder to retard orprevent the downward sliding of the brake collar upon retraction of thefirst stage piston.

As utilized in the prior art and referred to above, an annular chamber.17 is formed between the cylinder 1, the first stage piston 2 and theshoulders 16 and 19.

This chamber or space can be utilized to aid in retraction or as aholding device as shown in FIG. 4. To this end the chamber 17 is shutoff from the return line by means of an over pressure (pressure release)valve 18. A three way valve 21 is inserted into the line 20 leading fromthe chamber 17 which connects to the hydraulic system feed or returnline 23 and to a drain line 22. In the position shown, the valve 21permits the chamber 17 to exhaust only through the valve 18 (assumingvalve 24 is closed) thereby maintaining the pressure in the chamber 17at a value equal to the setting of the valve 18. The chamber 17 may bedrained, thereby permitting retraction of the first stage piston 5 byturning the valve 21 clockwise.

By maintaining the valve 21 in the position shown, the first stagepiston 5 is also prevented from extending further due to the pressure inthe chamber 17. Thus the second stage piston 10 is now permitted toextend by means of hydraulic pressure despite the fact that the firststage piston 5 has not extended to its maximum. Upon contact of the topof the second stage piston 10 with the roof, the valve 21 can be turned90 clockwise and the hydraulic fluid pressure permitted to extend thefirst stage piston 5 thus applying the required setting force.

Retraction of the first stage pistons can also be accomplished as shownin FIG. 4 by opening of the valve 24.

Referring once again to FIG. 5, the setting force for the prop can bepredetermined by use of a pressure release valve 32 which is set to openat a certain pressure. After the two pistons have been extended tosupport the roof 12 (shown in FIG. 3a), pressure from the roof istransmitted back through the pistons to the hYdI'ZiILlllC system throughthe valve 32.

The pistons are extended as heretofore mentioned by filling the chamber25 first until the first stage piston has been extended as far asdesired. The hydraulic fluid pressure then opens the check valve 26 byovercoming the pressure of the spring 28. The chamber 30 is then filledthereby extending the second stage piston 10 until it contacts the roof.Upon release of the mechanism restraining the first stage piston 5 thepressure in the chambers 25 and 30 equalizes permitting the valve 26 toclose whereby the setting force is applied solely to the first stagepiston 5 since the roof acting upon the second stage piston 10 maintainsthe valve 26 closed.

Upon retraction, the pressure in chamber 30 maintains the valve 26closed while both pistons retract as a unit through draining of thechamber 25. The base of the cylinder 33 is provided with an elevation 29and the valve 26 with an extension 27 so that as the base 15 of thefirst stage piston 5 comes to rest upon the elevation 29, its weightforces the valve 26 open permitting the chamber 30 to drain andretracting the second stage piston 10.

When the device is under pressure from above but still under hydraulicfluid pressure, the first stage piston will retract into the cylinderand cause the valve 26 to open whereby chamber 30 comes intocommunication with the pressure relief valve 32. Since the pressure inchamber 311 is less than the pressure in chamber 25, the valve 32 willpermit the hydraulic system to increase the pressure into chamber 25.This will extend the first stage piston 5 and close the valve 26. Duringthis the second stage piston 10 has retracted somewhat. With the valve26 closed, the pressure on the second stage piston 10 will retract theentire piston assembly thus causing the valve 26 to open and so onrepeating until the second stage piston is fully retracted. This cyclingretraction mechanism maintains a quite smooth descent by extraordinarilysimple means.

While the invention has been described in detail with reference to thespecific embodiments shown, various changes and modifications which fallwithin the spirit of the invention and scope of the appended claims willbecome apparent to the skilled artisan. The invention is, therefore,only intended to be limited by the appended claims or there equivalentswherein we have endeavored to claim all inherent novelty.

What is claimed is:

1. A multiple telescoping hydraulic prop having a single hydraulic fluidsystem to all telescoping pistons thereof wherein said prop containsmeans to restrain said largest piston from fully extending to itsmaximum prior to a smaller piston contacting a surface to be supportedby said prop; and check valve means :between two succestive pistonsoperative to permit flow of hydraulic fluid therethrough from saidhydraulic system into supporting relation with the smaller of saidsuccessive pistons and operative to permit flow of said hydraulic fluidfrom supporting relation with respect to said smaller piston to a sourceof said hydraulic fluid only when said larger piston is unsupported byhydraulic fluid.

2. A prop as claimed in claim 1 having a larger first stage and asmaller second stage piston; said first stage piston being restrainedfrom extending toits maximum until said second stage piston contactssaid surface.

3. A prop as claimed in claim 2 wherein said first stage piston isrestrained by means of chains.

4. A prop as claimed in claim 2 wherein said first stage piston isrestrained by means of springs.

5. A prop as claimed in claim 2 wherein said first stage piston isrestrained by means of a brake collar.

6. A prop as claimed in claim 2 wherein said first stage piston isrestrained by means of an hydraulic lock in the space between theexterior of said first stage piston and the interior of .a cylinder inwhich said first stage piston is housed.

7. A prop as claimed in claim :6 wherein said space communicates througha valve to a hydraulic system which operates said prop, said valve beingadjustable to isolate said space and to permit flow from said space tosaid system.

8. A prop as claimed in claim 2 wherein said first stage piston isrestrained by means of both chain and spring.

9. A double telescoping hydnaulic prop comprising a cylinder havingwalls, a base and inwardly projecting shoulders at the top thereof; .afirst stage piston ha'ving walls, a base, outwardly projecting shouldersat the base of said walls and inwardly projecting shoulders at the topthereof inside said cylinder; and a second stage piston having walls, abase and outwardly projecting shoulders at the base of said walls insidesaid first stage piston; said first stage piston base, said cylinderbase and said cylinder wa lls defining a first chamber; said first stagepiston base, said first stage piston walls and said second stage pistonbase forming a second chamber; a valve in said first stage piston baseadapted to provide communication between said first and said secondchambers; means to communicate said first chamber with a supply ofhydraulic fluid; and means to restrain said first stage piston fromextending to its maxi-mum prior to said second stage piston contacting asurface to be supported by said prop.

10. A prop as claimed in claim 9 wherein said first stage piston baseshoulder, said cylinder shoulder, said first stage piston walls and saidcylinder walls define a third chamber.

11. A prop as claimed in claim 10 wherein said third chambercommunicates with said hydraulic system through a valve means.

12. A prop as claimed in claim 9 wherein said valve between said firstand second chambers is a check valve characterized by the abilitythereof to maintain said second chamber sealed until said first stagepiston is substantially completely retracted.

13. A prop as claimed in claim 9 wherein said restraining means isadjustable to permit extension of said first stage piston anypredetermined amount less than to its maximum.

14. A prop as claimed in claim 11 wherein said valve means is operableexternally from said prop.

15. A prop as claimed in claim 9 wherein said hydraulic system isconnected to said prop through a pressure regulating valve.

16. A prop as claimed in claim 11 wherein said third chambercommunicates with a return hydraulic line through a pressure reliefvalve.

17. Method of supporting a member by means of a multiple telescopinghydraulic prop wherein said prop has a single hydraulic fluid system toall telescoping pistons thereof wherein said prop contains means torestrain said largest piston from fully extending to its maximum priorto 'a smaller piston contacting a surface to be supported by said prop;and check valve means between two successive pistons operative to permitflow of hydraulic fluid therethrough from said hydraulic system intosupporting relation with the smaller of said successive pistons andoperative to permit flow of said hydraulic fluid from supportingrelation with respect to said smaller piston to a source of saidhydraulic fluid only when said larger piston is unsupported by hydraulicfluid, which method comprises exerting hydraulic pressure upon thelargest piston to extend such until said restraining means preventsfurther extension; exerting hydraulic pressure on each successivelysmaller piston in turn until the extension of each is restrained;exerting hydraulic pressure upon the smallest piston until it contactsthe member being supported; and exerting additional hydraulic pressureupon the assembly to set the assembly against the member.

18. The method claimed in claim 17 wherein said additional hydraulicpressure overrides said restraining means.

19. The method claimed in claim 18- wherein there are two pistons.

20. The method claimed in claim 17 wherein a valve means communicatesbetween a first reservoir serving to exert hydraulic pressure on alarger piston .and a second reservoir serving to exert hydraulicpressure on a next smaller piston; said valve means being within thebase of said larger piston and containing a shaft operable to open saidvalve which extends beyond said base; said valve being opened by saidlarger piston base approaching its fully withdrawn position and saidshaft making contact with the member against which said fully withdrawnlarger piston rests.

References Cited by the Examiner UNITED STATES PATENTS 1,928,533 9/1933Goss 254-93 3,145,964- 8/ 1964 Groetschel. 3,241,801 3/1966 Wilkenloh et.al. 248354 FOREIGN PATENTS 972,317 10/ 1964 Great Britain.

CLAUDE A. LE ROY, Primary Examiner.

1. A MULTIPLE TELESCOPING HYDRAULIC PROP HAVING A SINGLE HYDRAULIC FLUIDSYSTEM TO ALL TELESCOPING PISTONS THEREOF WHEREIN SAID PROP CONTAINSMEANS TO RESTRAIN SAID LARGEST PISTON FROM FULLY EXTENDING TO ITSMAXIMUM PRIOR TO A SMALLER PISTON CONTACTING A SURFACE TO BE SUPPORTEDBY SAID PROP; AND CHECK VALVE MEANS BETWEEN TWO SUCCESTIVE PISTONSOPERATIVE TO PERMIT FLOW OF HYDRAULIC FLUID THERETHROUGH FROM SAIDHYDRAULIC SYSTEM INTO SUPPORTING RELATION WITH THE SMALLER OF SAIDSUCCESSIVE PISTONS AND OPERATIVE TO PERMIT FLOW OF SAID HYDRAULIC FLUIDFROM SUPPORTING RELATION WITH RESPECT TO SAID SMALLER PISTON TO A SOURCEOF SAID HYDRAULIC FLUID ONLY WHEN SAID LARGER PISTON IS UNSUPPORTED BYHYDRAULIC FLUID.